In an industrial robot, a linear and rotary actuator is sometimes embedded that makes the movable body move linearly in the Z-axis direction and rotate around the Z axis in the θ direction. For example, a head shaft of a chip mounter is required to make the movable body such as an absorption pad for absorption of an electronic component or machine tool move linearly in the Z-axis direction and rotate around the Z axis. Linear movement of the movable body in the Z-axis direction is needed in embodiment of the electronic component on a surface of a printed board and rotation of the movable body in the θ direction is needed in positioning of the rotation angle of the electronic component.
As a linear and rotary actuator capable of linear and rotary movement, the patent literature 1 discloses a linear and rotary pulse motor having a linear pulse motor and a rotary pulse motor connected to each other in the axial direction. In this linear and rotary pulse motor, a rotor of the rotary pulse motor is a hollow shaft and a spline bearing with a rotation stopper mechanism is arranged in this hollow shaft. The mover shaft of the linear pulse motor passes through the spline bearing slidably and linear pulse motor moves the mover shaft linearly in the Z-axis direction. An output of the rotary pulse motor in the rotary direction is transmitted to the mover shaft via the spline bearing. The mover shaft is rotated in the θ direction by the rotary pulse motor.
As this linear and rotary pulse motor adopts a linear stepping motor having comb teeth of the mover face comb teeth of the stator, it is necessary to control an air gap between the mover and the stator to be a small fixed value.
In order to facilitate control of the air gap between the mover and the stator, the patent literature 2 discloses a linear and rotary pulse motor that adopts a linear synchronization motor instead of the linear pulse motor. This linear synchronization motor has a mover shaft having one or more permanent magnets magnetized in the axial direction and a stator having a plurality of coils stacked in the axial direction. An end of the linear synchronization motor in the axial direction is connected to the rotary motor. Torque of the rotary motor is transmitted to the mover shaft via the sliding bearing. In order to transmit rotation to the mover shaft, a guide hole of the sliding bearing is formed to have a rectangular cross section.